1. Field of the Invention
The present invention relates to a magnetic bubble memory device adapted to operate a plurality of magnetic bubble memory chips in parallel.
2. Description of the Prior Art
As compact and high-density nonvolatile memory devices with high reliability, magnetic bubble memory devices have been applied to various electronic apparatus.
Because such magnetic bubble memory devices, which are serial type memory devices, perform writing-in and reading-out of data by transferring magnetic bubbles, their data transmission speeds depend on the transfer speed of the magnetic bubbles. Accordingly, the simplest way to increase the data transmission speed is to increase the driving speed of magnetic bubbles, i.e., to increase the rotation magnetic field frequency.
It is, however, difficult to obtain a high driving speed above 500 kHz, because an increase in the driving frequency is inevitably accompanied by an increase in the loss in the coil by which the rotation magnetic field is produced. Accordingly, such a method for increasing the data transmission speed of a magnetic bubble memory device as a memory system has been practiced by employing a plurality of magnetic bubble chips and operating them in parallel.
In such a conventional magnetic bubble memory device, a plurality of magnetic bubble chips are provided with a controller, a clock generator and a timing generator employed in common so as to be simultaneously driven by means of the same clock.
Such a conventional device, however, requires a custom-designed mounting board for each application system in order to cope with the demand for various data transmission speeds and data formats of respective application systems; accordingly, the device has poor extensibility and brings about a rise in cost.